This invention relates to a lens holder driving device and, in particular, to a lens holder driving device capable of picking up a static image without blurry images by stabilizing the blurry images (movement) occurring upon shooting the static image using a miniature camera for a mobile terminal.
Hitherto, various lens holder driving devices has been proposed which are capable of taking photographs with a high degree by stabilizing blurry images on an image-forming surface although there are blurry images (movement) upon shooting the static image.
As image stabilizing methods, “optical methods” such as a sensor shift method or a lens shift method and “a software stabilizing method” for stabilizing the blurry images using image processing by software are known. An image stabilizing method introduced in the mobile terminal mainly adopts the software stabilizing method.
The software stabilizing method is disclosed, for example, in Japanese Unexamined Patent Application Publication No. H11-64905 (JP-A-11-064905) (which will be also called Patent Document 1). The software stabilizing method disclosed in Patent Document 1 comprises the steps of removing noise components from detected results of detection means, of calculating, from a detected signal in which the noise components are removed, particular information necessary to stabilize image blurred due to an image blurring of an image pickup device, thereby making a picked-up image be at a standstill in a nonshaking state where the image pickup device remains at rest.
However, the image stabilizing method of “the software stabilizing method” disclosed in the Patent Document 1 has a problem so that image quality degrades in compassion with the “optical method” which will later be described. In addition, the image stabilizing method of the software stabilizing method has disadvantage so that a taking time interval becomes longer because processing of the software is included therein.
Therefore, as the image stabilizing methods, request of “the optical methods” are on the increase with higher pixels in recent years. As the image stabilizing methods of “the optical methods”, “a sensor shift method”, “a lens shift method”, and “an optical unit tilt method” are known.
The sensor shift method is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2002-274242 (JP-A-2002-274242) (which will be also called Patent Document 2). A digital camera disclosed in Patent Document 2 has structure in which an image pickup device (CCD) can shift with a center at a reference position (center) by an actuator. The CDD is disposed in a CCD moving portion. The CCD can move in a X-Y plane orthogonal to a Z-axis by the CCD moving portion. The CCD moving portion mainly comprises three members: a base plate fixed to a housing; a first slider moving with respect to the base plate in a direction of an X-axis; and a second slider moving with respect to the first slider in a direction of a Y-axis.
However, in “the sensor shift method” as disclosed in Patent Document 2, the CCD moving portion (a movable mechanism) becomes large. It is therefore difficult in terms of size (outer dimensions, a height) to adopt the image stabilizer of the sensor shift method to a miniature camera for a mobile phone.
Now, the description will proceed to the lens shift method. By way of illustration, Japanese Unexamined Patent Application Publication No. 2009-145771 (JP-A-2009-145771) (which will be also called Patent Document 3) discloses an image stabilizing device including an image stabilizing unit for driving a correction lens. The image stabilizing unit comprises a base plate serving as a fixed member, a movable mirror barrel holding the correction lens movably, three balls sandwiched between the base plate and the movable mirror barrel, and a plurality of elastic bodies for elastically supporting the movable mirror barrel with respect to the base plate, two coils fixed to the base plate, and two magnets fixed to the movable mirror barrel.
In addition, Japanese Unexamined Patent Application Publication No. 2006-65352 (JP-A-2006-065352) (which will be also called Patent Document 4) discloses “an image stabilizing device” for stabilizing image blurred by moving and controlling a particular lens group (which will later be called “a correction lens”) among an image pickup optical system comprising a plurality of lens groups in two directions orthogonally crossing to each other within a plane perpendicular to an optical axis. In the image stabilizing device disclosed in Patent Document 4, the correction lens is movably supported with respect to a fixed frame up and down (in a pitch direction) and from side to side (in a yaw direction) via a pitching moving box and a yawing moving frame.
Japanese Unexamined Patent Application Publication No. 2008-26634 (JP-A-2008-026634) (which will be also called Patent Document 5) discloses “an image stabilizing unit” including a stabilizing optical member for stabilizing blurry images formed by an imaging optical system by being moved to a direction crossed with an optical axis of the imaging optical system. In the stabilizing optical member disclosed in Patent Document 5, a lens holding flame for holding a correction lens is movably supported with respect to a receiving barrel in a pitch direction and a yaw direction via a pitch slider and a yaw slider.
Japanese Unexamined Patent Application Publication No. 2006-215095 (JP-A-2006-215095) (which will be also called Patent Document 6) discloses “an image stabilizing device” which is capable of moving a correction lens by small driving force and which is capable of rapidly and accurately stabilizing the blurry images. The image stabilizing device disclosed in Patent Document 5 comprises a holding frame holding the correction lens, a first slider for slidably supporting the holding frame in a first direction (a pitch direction), a second slider for slidably supporting the holding frame in a second direction (a yaw direction), a first coil motor for driving the first slider in the first direction, and a second coil motor for driving the second slider in the second direction.
Japanese Unexamined Patent Application Publication No. 2008-15159 (JP-A-2008-015159) (which will be also called Patent Document 7) discloses a lens barrel comprising an image stabilizing optical system provided to enable to move in a direction orthogonal to an optical axis. In the image stabilizing optical system disclosed in Patent Document 7, a movable VR unit disposed in a VR body unit holds a correction lens (a third lens group) and is disposed so as to enable to move in a X-Y plane orthogonal to the optical axis.
Japanese Unexamined Patent Application Publication No. 2007-212876 (JP-A-2007-212876) (which will be also called Patent Document 8 and which corresponds to U.S. Pat. No. 7,619,838) discloses “an image stabilizer” which is capable to stabilize image blurred by performing control so that the optical axis of a correction lens held in a moving frame may be aligned with the optical axis of a lens system by moving the correction lens in first and second directions orthogonal to the optical axis of the lens system by driving means.
Japanese Unexamined Patent Application Publication No. 2007-17957 (JP-A-2007-017957) (which will be also called Patent Document 9) discloses “an image stabilizer” for stabilizing image blurred by driving a correcting lens for stabilizing the blurry images that are formed by a lens system by operation of a lens driving part in a first direction and a second direction which are perpendicular to an optical axis of the lens system and which are perpendicular to each other. In the image stabilizer disclosed in Patent Document 9, the lens driving part is provided at one side of the correcting lens in the direction perpendicular to the optical axis.
Japanese Unexamined Patent Application Publication No. 2007-17874 (JP-A-2007-017874) (which will be also called Patent Document 10 and which corresponds to U.S. Pat. No. 7,650,065) discloses “an image stabilizer” which is capable to stabilize blurry images by performing control so that the optical axis of a correction lens held in a moving frame may be aligned with the optical axis of a lens system by moving the correction lens in first and second directions which are perpendicular to the optical axis of the lens system and which are perpendicular to each other. The image stabilizer disclosed in Patent Document 10 comprises driving means including a coil and a magnet which can be relatively moved. One of the coil and the magnet is fixed to a moving frame while another is fixed to a supporting frame for supporting a movable frame movably. In addition, the image stabilizer disclosed in Patent Document 10 comprises a first Hall element for detecting position information related to the first direction of the correction lens by detecting a magnetic force of the magnet and a second Hall element for detecting position information related to the second direction of the correction lens by detecting the magnetic force of the magnet.
Any of the image stabilizers (the image stabilizing devices) of “the lens shift method” disclosed in the above-mentioned Patent Documents 3 to 10 has structure for moving and adjusting the correction lens in a plane perpendicular to the optical axis. However, such image stabilizers (the image stabilizing devices) have problems in which structure is complicated and they are unsuited for miniaturization. That is, like in the above-mentioned image stabilizer of the sensor shift method, it is difficult in terms of size (outer dimensions, a height) to adopt the image stabilizer of the lens shift method to the miniature camera for the mobile phone.
In order to resolve the above-mentioned problems, an image stabilizer (an image stabilizing device) has been proposed which stabilizes blurry images (image blurred) by swinging a lens module (a camera module) for holding a lens and a pickup device (an image sensor) in itself. Such a method will be referred to herein as “an optical unit tilting method”.
Now, the description will proceed to “the optical unit tilting method”.
By way of illustration, Japanese Unexamined Patent Application Publication No. 2007-41455 (JP-A-2007-041455) (which will be also called Patent Document 11) discloses “an image stabilizer of an optical device” comprising a lens module for holding a lens and an imaging element, a frame structure for rotatably supporting the lens module by rotary shafts, driving means (actuators) for rotating the lens module with respect to the frame structure by imparting driving force to driven parts (rotors) of the rotary shafts, and energizing means (leaf springs) for energizing the driving means (the actuators) to the driven parts (the rotors) of the rotary shafts. The frame structure comprises an inner frame and an outer frame. The driving means (the actuators) is disposed so as to be in contact with the driven parts (the rotors) of the rotary shafts from directions perpendicular to an optical axis. The driving means (the actuators) comprises a piezoelectric element and an action part of the rotary shafts side. The action part drives the rotary shafts by vertical vibrations and bending vibrations of the piezoelectric element.
However, it is necessary for the image stabilizer of “the optical unit tilting method” disclosed in Patent Document 11 to cover the lens module with the frame structure comprising the inner frame and the outer frame. As a result, there is a problem in which the image stabilizer becomes large.
In addition, Japanese Unexamined Patent Application Publication No. 2007-93953 (JP-A-2007-093953) (which will be also called Patent Document 12) discloses “an image stabilizer for a camera” for stabilizing blurry images upon shooting a static image by accommodating a camera module in which a pickup lens and an image sensor are integrated in a housing, by swingably mounting the camera module in housing at a center of first and second axes which are orthogonal to a pickup optical axis and which cross each other at right angles, and by controlling the attitude of the camera module as a whole in the housing in response to a shake of the housing detected by a shake sensor. The image stabilizer for the camera disclosed in Patent Document 12 comprises an intermediate frame for swingably supporting an inner frame in which the camera module is fixed at the first axis as a center from the outside thereof, an outer frame, fixed to the housing, for swingably supporting the intermediate frame at the second axis as a center from the outside thereof, first driving means, mounted inside the intermediate frame, for swinging the inner frame around the first axis in response to a shake signal from a shake sensor (a first sensor module for detecting a shake in a pitch direction), and second driving means, mounted inside the outer frame, for swinging the intermediate frame around the second axis in response to a shake signal from a shake sensor (a second sensor module for detecting a shake in a yaw direction). The first driving means comprises a first stepping motor, a first reduction gear train for reducing a rotation thereof, and a first cam for swinging the inner frame through a first cam follower provided to the inner frame by rotating it integral with a final stage gear. The second driving means comprises a second stepping motor, a second reduction gear train for reducing a rotation thereof, and a second cam for swinging the intermediate frame through a second cam follower provided to the intermediate frame by rotating it integral with a final stage gear.
However, also in the image stabilizer of “the optical unit tilting method” disclosed in Patent Document 12, it is necessary to cover the camera module with the inner frame, the intermediate frame, and the outer frame. As a result, the image stabilizer becomes large. Furthermore, inasmuch as there are the rotary axes in “the optical unit tilting method”, there is a problem in which friction is produced between a hole and an axis and it results in exhibiting hysteresis.
Furthermore, Japanese Unexamined Patent Application Publication No. 2009-288770 (JP-A-2009-288770) (which will be also called Patent Document 13 and which corresponds to US 2011/097062) discloses an optical photography device which is capable of reliably stabilizing blurry images by improving the structure of an photography unit drive mechanism for stabilizing the blurry images in an photography unit. The optical photography device disclosed in Patent Document 13 comprises, inside a fixed cover, the photography unit (a movable module) and an image stabilizing mechanism for stabilizing blurry images by displacing the photography unit. The photography unit is for moving a lens along a direction of an optical axis. The photography unit comprises a moving body for holding the lens and a fixed aperture therein, a lens driving mechanism for moving the moving body in the direction of the optical axis, and a supporting body in which the lens driving mechanism and the moving body are mounted. The lens driving mechanism comprises a lens driving coil, a lens driving magnet, and a yoke. The photography unit is supported to a fixed body via four suspension wires. At two positions on both sides sandwiching the optical axis, a first photography unit drive mechanism and a second photography unit drive mechanism, which are for stabilizing the blurry images, are respectively provided as a pair. In each of their photography unit drive mechanisms, a photography unit drive magnet is held in a movable body side while a photography unit drive coil is held in a fixe body side.
However, in the optical photography device of “the optical unit tilting method” disclosed in Patent Document 13, it is necessary to use the photography unit drive magnets as well as the lens drive magnet. As a result, there is a problem in which the optical photography device becomes large.
In addition, Japanese Unexamined Patent Application Publication No. 2011-107470 (JP-A-2011-107470) (which will be also called Patent Document 14) discloses a lens driving device which is capable of not only driving a lens in a direction of an optical axis but also stabilizing blurry images. The lens driving device disclosed in Patent Document 14 comprises a first holding body for holding the lens so as to be movable it in the direction of the optical axis (Z direction), a second holding body for holding the first holding body so as to be movable it in the Z direction, a fixed body for holding the second holding body so as to be movable it in a direction which is substantially orthogonal to the Z direction, a first driving mechanism for driving the first holding body in the Z direction, a second driving mechanism for driving the second holding body in an X direction, and a third driving mechanism for driving the second holding body in a Y direction. The first holding body is supported to the second holding body by a first supporting member made of an elastic material so as to be movable in the Z direction. The second holding body is supported to the fixed body by a second supporting member made of an elastic material so as to be movable in the Z direction. The first driving mechanism comprises a first drive coil and a first drive magnet, the second driving mechanism comprises a second drive coil and a second drive magnet, and the third driving mechanism comprises a third drive coil and a third drive magnet.
In the lens driving device disclosed in Patent Document 14, three kinds of driving mechanisms consisting of the first through the third driving mechanism require as driving mechanisms, and each of the first through third driving mechanisms comprises a coil and a magnet, independently. Therefore, there is a problem in which the number of parts is increased.
Japanese Unexamined Patent Application Publication No. 2011-113009 (JP-A-2011-113009) (which will be also called Patent Document 15) discloses a lens driving device which uses a plurality of wires as the second supporting member and which comprises a buckling prevention member for preventing buckling of the wires while its basic structure is similar to the lens driving mechanism disclosed in the above-mentioned Patent Document 14. Each wire is formed in a straight line and the second holding member is supported by the wires so as to be movable in the direction which is substantially orthogonal to the Z direction. The buckling prevention member is made of an elastic member and becomes elastically deformed in the Z direction at a force smaller than a buckling load of the wire. More specifically, the buckling prevention member comprises a wire fixed portion formed to a leaf spring for the first supporting member. When a force applies to a movable part such as the second holding body downwards, the wire fixed portion becomes elastically deformed downwards.
In also the lens driving device disclosed in Patent Document 15, in the manner similar to the lens driving device disclosed in Patent Document 14, there is a problem in which the number of parts is increased. In addition, the lens driving device disclosed in Patent Document 15 merely prevents the wires from buckling because the force applies to the wires in a direction to compress. In other words, the lens driving device disclosed in Patent Document 15 does not take into account in a case where the wires may rupture because a force applies to the wires in a direction to extend.
Therefore, two of the present co-inventors proposed an image stabilizer which is capable of miniaturizing and lowering a height by sharing a permanent magnet for an auto-focusing (AF) lens driving device as a permanent magnet for the image stabilizer (see, Japanese Unexamined Patent Application Publication No. 2011-65140 (JP-A-2011-065140) (which will be also called Patent Document 16)).
The image stabilizer disclosed in Patent Document 16 is called an image stabilizer of “a barrel shift method” because camera shake is corrected by moving a lens barrel received in an AF lens driving device in itself. In addition, the image stabilizers of “the barrel shift method” are classified into “a moving magnet method” in which the permanent magnet moves (is movable) and “a moving coil method” in which the coil moves (is movable).
Patent Document 16 discloses, as the image stabilizer of “the moving magnet method” in a second exemplary embodiment thereof”, an image stabilizer which is provided with a permanent magnet comprising four first permanent magnet pieces and four second permanent magnet pieces which are disposed so as to apart from up and down in a direction of an optical axis and which is provided with a stabilizer coil disposed between the upper four first permanent magnet pieces and the lower four second permanent magnet pieces. That is, the second exemplary embodiment comprises the image stabilizer of “the moving magnet method” including the permanent magnet comprising eight permanent magnet pieces in total.
In the image stabilizer disclosed in Patent Document 16, a base is disposed so as to apart from at a bottom portion of the auto-focusing lens driving device and a plurality of suspension wires have one ends which are fixed to the base at outer regions thereof. The plurality of suspension wires has other ends which are firmly fixed to the auto-focusing lens driving device.
In the image stabilizer disclosed in Patent Document 16, the other ends of the plurality of suspension wires are firmly fixed to the auto-focusing lens driving device. It is therefore feared that the plurality of suspension wires may fracture in a case where the plurality of suspension wires are subjected to force in a direction to extend due to drop impact of the image stabilizer or the like.
Japanese Unexamined Patent Application Publication No. 2011-85666 (JP-A-2011-085666) (which will be also called Patent Document 17) also discloses a lens driving device which shares an AF control magnet as an image stabilizer control magnet. The lens driving device disclosed in Patent Document 17 comprises a lens holder including a first coil (an AF coil) disposed at an outer periphery of a lens, a magnet holder configured to fix a magnet having a first surface facing the first coil, springs for supporting the lens holder so as to couple the lens holder with the magnet holder and also so that the lens holder is moved with respect to the magnet in a direction of an optical axis, and a base member configured so that a second coil (an image stabilizer coil) is fixed to face a second surface of the magnet that is perpendicular to the first surface thereof. A lens holding unit, which comprises the lens holder, the magnet, the magnet holder, and the springs, is held so as to be relatively movable in a direction perpendicular to the optical axis relative to the base member.
Patent Document 17 discloses the lens driving device as a six exemplary embodiment in which a position detection sensor is disposed at a clearance of the image stabilizer coil wound. A Hall element is used as the position detection sensor. In addition, the lens holding unit is held by four suspension wires which are disposed to a fixed portion at four corners thereof. That is, the four suspension wires have one ends fixed to the four corners of the fixed portion and other ends which are firmly fixed to the lens holding unit.
In also the lens driving device disclosed in Patent Document 17, the other ends of the four suspension wires are firmly fixed to the lens holding unit. As a result, in the manner similar to the image stabilizer disclosed in Patent Document 16, it is feared that the four suspension wires may fracture in a case where the four suspension wires are subjected to force in a direction to extend due to drop impact of the lens driving device or the like.
On the other hand, in the manner which is describe above, the lens driving device disclosed in Patent Document 15, by providing the buckling prevention member, prevents buckling of the wires although the force applies to the wires in the direction to compress due to drop impact or the like. However, the lens driving device disclosed in Patent Document 15 does not take into account the fear of fracture of the wires in a case where force applies to the wire in a direction to extend due to drop impact or the like.